Sludge Metal

Less an "official" genre than a particular term with some acceptance,
sludge metal is characterized by crushingly heavy riffing (often more
distorted than normal, even for metal), with hardcore-ish vocals the norm.
No one band is really considered a founder of the style, but one geographic
area dominates the field, and that is New Orleans, as many of the top
bands
(Crowbar,
Eyehategod,
and
Soilent Green,
to name three)
hail from that city.